SMOKING will cut at least ten years from your life, the first ever long-term Australian study has found.

And even light smoking - consuming ten or fewer cigarettes a day - will double your risk of death.

Pack-a-day smokers have a fourfold greater risk of dying early, a study of the 200,000 Australians aged over 45 taking part in the Sax Institute's 45 and Up study has found.

The earlier you quit smoking, the better the outcome, the study found.

Until now health experts have been relying on overseas studies about the effects of smoking; this is the first large scale long term Australian study on tobacco use.

And the results from the Australian study are more alarming, showing two thirds of deaths in current smokers can be directly attributed to smoking.

International studies estimate only half the deaths in current smokers can be attributed to their smoking.

"We all know that smoking is bad for your health, but until now we haven't had direct large-scale evidence from Australia about just how bad it is," said the 45 and Up study director, Professor Emily Banks.

"People don't realise how damaging even light smoking is for your health - for cancer, heart disease, lung disease and a range of other conditions," said study co-author Associate Professor Freddy Sitas from Cancer Council NSW.

Within time the researchers hope to be able to reveal what caused the deaths of the patients in the study.

Smoking prevalence in Australian peaked in 1945 for men and 1978 for women, and Australia is now experiencing a "mature epidemic" where the full impact of smoking on health is only just being realised, Professor Banks said.

The Australian Health Survey reported in 2011-12 that eight million Australian adults had smoked at some time in their lives and 3.1 million were current smokers.

Smoking rates have been falling over the past decade from 27 per cent to 20 per cent for males and from 21 per cent to 16 per cent for females.

The 45 and Up Study is following the health and ageing of a quarter of a million Australians and is the largest ongoing study of healthy ageing in the Southern Hemisphere.

It measure not just smoking rates but how obesity, alcohol and other factors impact health.